This study examines the natural course of age-related changes in muscular strength and determines the relationship of age and strength levels to body composition and health status. The relationship of age to maximal force production (strength) of the upper and lower body musculature during the concentric (shortening) and eccentric (elongation) phases of movement are presently being established. In addition, strength measures are being assessed at slow, fast and zero (isometric) speeds to determine if there is a preferential loss of force at fast speeds with age. This information will be related to the selective atrophy of type II fibers that occurs with age. Analyses of changes in force production in the prime mover is being compared to changes in the antagonist muscle group to determine if muscle balance is affected with age. In addition, the angle of greatest force production is being assessed to determine if this angle changes with age. New testing equipment has been purchased and a new protocol has been established for this project. Over 200 male and female subjects from the 20s through the 80s have been tested so far this year.